The invention relates generally to signal analysis devices and, more specifically, to a method and apparatus for providing multiple presentations of contemporaneously acquired data.
In a conventional digital storage oscilloscope (DSO), signal acquisition hardware is typically based upon one of two architectures that are used to achieve a desired time interval per sample, as requested by a user via a time/division selection input on the DSO. A first architecture controls a clocking input to an analog to digital (A/D) converter via the time/division setting. In this manner, the analog signal digitized by the A/D converter is digitized at a clock rate controlled by the time/division setting, such that the A/D converter is clocked at the correct speed to generate the desired number of samples. In a second architecture, the A/D converter is always clocked at a maximum sample rate to produce a maximum number of samples. The maximum number of samples are then decimated to reduce the sample rate to match a user""s requested sample interval.
The decimation function described above may be implemented using a variety of algorithms. In some digital storage oscilloscopes manufactured by Tektronix, Inc. of Beaverton, Oreg., three decimation modes are provided; namely, a xe2x80x9cnormalxe2x80x9d mode that provides sub-sampling, a xe2x80x9cpeak-detectxe2x80x9d mode that provides for the detection of minimum and maximum samples and a xe2x80x9chigh resolutionxe2x80x9d mode that utilizes a box-car averaging algorithm.
The above-described decimation algorithms and other decimation algorithms tend to be mutually exclusive (i.e., only one type of decimation may be selected at one time) due, for example, to bandwidth limitations associated with memory within the digitizing measurement device.
These and other deficiencies of the prior art are addressed by the present invention of a method and apparatus enabling the concurrent operation of multiple decimators within a digitizing measurement device such as a digital storage oscilloscope. The multiple decimators provide multiple processed sample streams that may be used for a composite presentation of input signal data in a manner tending to be more meaningful to a test equipment user.
The subject invention is adapted, in one embodiment, to an apparatus comprising an analog to digital (A/D) converter for digitizing a signal to produce a stream of samples, a plurality of decimators, for concurrently processing the stream of samples according to respective decimation modes to produce respective decimated sample streams, and a memory, for storing the decimated sample streams.